As part of a program to explore technological options for the transition to a renewable energy future, we develop scenarios for 100% renewable generation to meet current electricity demand in the five Australian states and one territory spanned by the National Electricity Market (NEM). The preliminary simulations reported here cover a scenario for the year 2010, where electricity demand is met by a renewable generation mix based on concentrating solar thermal (CST) power with thermal storage, wind, photovoltaics (PV), existing hydro, and peaking gas turbine plants running on biofuels. Generation from these sources in 2010 is simulated using meteorological records for that year. A 100% renewable mix for the NEM is found to be technically feasible for the year 2010, meeting the NEM reliability standard with only six hours in the year where demand is unmet. However, this is achieved with a high capacity (24 GW) of peaking gas turbine plants to cover periods of insufficient power from other sources, typically winter evenings. Increasing the solar multiple of CST plants is helpful in allowing more energy to be captured and stored during winter, marginally reducing the required capacity of gas turbines. Overall, meeting evening peak periods in the winter months remains the principle challenge.